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Research about Eureka, Nevada

Source-linked reports with geographic coverage including Eureka, Nevada.

8 recordsLinked to original sources
USGS2003

Structural controls on Carlin-type gold mineralization in the gold bar district, Eureka County, Nevada

The Gold Bar district in the southern Roberts Mountains, 48 km northwest of Eureka , Nevada , contains one main deposit ( Gold Bar ), five satellite deposits, and other resources. Approximately 0.5 Moz of gold have been recovered from a resource of 1,639,000 oz of gold in Carlin - type gold deposits in lower plate, miogeoclinal carbonate rocks below the Roberts Mountains thrust. Host rocks are unit 2 of the Upper Member of the Devonian Denay Formation and the Bartine Member of the McColley Canyon Formation. Spatial and temporal relations between structures and gold mineralization indicate that both pre-Tertiary and Tertiary structures were important controls on gold mineralization . Gold mineralization occurs primarily along high-angle Tertiary normal faults, some of which are reactivated reverse faults of Paleozoic or Mesozoic age. Most deposits are localized at the intersection of northwest- and northeast-striking faults. Alteration includes decalcification, and to a lesser extent, silicification along high-angle faults. Jasperoid (pervasive silicification), which formed along most faults and in some strata-bound zones, accounts for a small portion of the ore in every deposit. In the Gold Canyon deposit, a high-grade jasperoid pipe formed along a Tertiary normal fault which was localized along a zone of overturned fault-propagation folds and thrust faults of Paleozoic or Mesozoic age.

Nevada↗
USGS1992

Mapping thermal maturity in the Chainman shale, near Eureka, Nevada, with Landsat Thematic Mapper images

The purpose of this study was to determine if there is a correlation between measurements of organic matter (OM) maturity and laboratory measurements of visible and near-infrared spectral reflectance, and if Landsat Thematic Mapper (TM) images could be used to map maturity. The maturity of Mississippian Chainman Shale samples collected in east-central Nevada and west-central Utah was determined by using vitrinite reflectance and Rock-Eval pyrolysis. To establish the relations between maturity and spectral reflectance in the visible and near-infrared (VNIR) wavelength region, VNIR reflectance spectra of fresh and weathered whole-rock sample surfaces were measured in the laboratory. The spectra were convolved digitally with the Landsat TM filter band passes to facilitate th analysis, especially the relative sensitivities of individual band passes and ratios of band passes to spectral reflectance variations related to OM maturity. With increasing maturity, overall VNIR diffuse reflectance and mineral-absorption-feature intensities decrease, and the shape of the spectra changes from concave-downward to nearly flat. The spectral shape differences between mature and supermature samples remains distinctive in reflectance spectra of weathered surfaces. TM 4/TM 5 values correspond well to vitrinite reflectance and hydrogen index variations, and therefore this ratio was used to evaluate a TM image of the Eureka, Nevada, area for mapping thermal maturity differences in the Chainman Shale. First, the contribution of vegetation to the TM response was minimized using a linear regression technique, and then a TM 4/TM 5 density-sliced image was produced. Field evaluation of the TM 4/TM 5 density-sliced image shows that all the high values in the Chainman Shale, which correspond to high maturity, are located in the Diamond Mountains; in contrast, Chainman Shale in the northwestern Pancake Range exhibits low to moderate values. These results are consistent with published local maturity determinations. Locally, the presence of limonitic arenaceous exposures and colluvium causes anomalously low TM 4/TM 5 values, but these areas can be identified in TM images because of their diagnostic VNIR reflectance spectra.

Nevada↗
USGS1985

Geology of the Carlin gold deposit, Nevada

This report describes the geology of the Carlin gold deposit and the Lynn mining district, including an area of about 80km 2 in northern Eureka County, Nev. (fig. 1). The Carlin mine is located in secs. 13 and 14, T.35N., R.50E., at an elevation of 6,400 ft near the crest of the Tuscarora Mountains. The map area (pl. 1), centered approximately on the Carlin mine, measures about 10km east-west by 8km north-south and forms approximately the south two-thirds of the Rodeo Creek NE. 7{1/2}-minute quadrangle. Boundaries for the map area are meridians 116°15'00" and 116°22'30" W. and parallels 40°52'30" and 40°57'30"N. The Carlin mine is accessible by an asphalt-surfaced road extending about 35km northward from the town of Carlin, Nev., which is on U.S. Highway 40. A secondary improved road extends from the Carlin mine westward into Boulder Valley and connects with both State Highway 18 to the north and U.S. Highway 40 to the south near the town of Dunphy. An unimproved road extends from the Carlin mine northward, along the west side of Little Boulder Basin, to the Blue Star mine, and continues northward and westward along Rodeo Creek to connect with a graded road extending northeastward along Boulder Valley. Numerous unimproved roads have been built to provide access to the different mining prospects.

Nevada↗
USGS1975

The Oligocene volcanic center at Eureka, Nevada

A volcanic center covering an area of about 80 km 2 near Eureka, Nev., and active in the early Oligocene, is characterized by rhyolitic, rhyodacitic. and andesitic pyroclastic rocks, lava flows, and shallow intrusive bodies. These rocks were emplaced as intertonguing and interpenetrative units during a 5-m.y. interval; most of the volcanism was in the last 3 million years of this period (36 to 33 m.y. ago).

Nevada↗